Electric switch



April 20, 1937. R. N. RowE ELECTRICk SWITCH Filed Jan. l5, 1936 INVENTOR AYMND N. Rows,

BY A

ATTORNEY Patented Apr. 20, 1937 PATENT OFFICE ELECTRIC SWITH Raymond N. Rowe,

Plainvlle, Qonn., assigner to The Trumbull Electric Manufacturing Company, Plainville, 60ml.,

necticut a corporation or' @ou- Application January i3, 11936, Serial No. 58,840

5 (Claims. (GCH. 20H- 134) My invention relates to the contact mechanisms of electric devices such as switches and protective devices and has for its main object to maintain eiective engagement between the contact members, even when they become heated or otherwise weakened.

A common type switch employs spring contact jaws between which a movable blade-like switch member or contact is inserted. Frequently these spring jaws become weakened by long continued heating or by repeated opening and closing of the circuit. The weakening of the contact pressure of course tends to increase the resistance and cause overheating of the switch.

I have sought to prevent or overcome this diiculty in a simple and inexpensive manner.

In carrying out the invention I mount' the spring jaws in an insulating base and provide bimetallic springs which are constructed so as topress the jaws against the inserted switch blade and increase the contact pressure as the temperature rises. I have also provided a means -to prevent the jaws from being pressed too closely together, making it possible to introduce the switch blade regardless of the amount that the thermal elements are flexed by heating.

Details of a preferred form of the invention are shown and described.

Fig. l is a sectional view of a switch embodying my invention with the parts in open circuit position,

Fig. 2 is a fragmentary sectional view on a larger scale showing the switch in closed circuit position.

Fig. 3 is a sectional view of the movable switch member.

' Fig. 4 is a perspective view of the parts of a staf tionary contact.

Fig. 5 is a perspectiveview of the movable switch element.

The general construction of the particular switch shown is more fully described, shown and claimed in my companion application Serial Number 56,406 filed December 28th, 1935.

The insulating base 6 carries the terminal bars 1 and 8 and they in turn support the contact jaws 9 and I0 within the recesses Il and I2.

'I'he movable contact or switch member il is of U-shape and is carried by an insulating block Preferably this switch member is loosely mounted and resiliently held in its proper position by a spring I6 so that it can better adapt itself to the spring jaws.

The invention is shown as embodied in an enclosed type switch'having a box 20 with a cover 2l hinged at 22 andprovided with a latch or sealing device 23.

The block l5 and its switch member M are carried by a slide 24 which is supported in the cover and provided with an external handle 25 for moving the slide. In the position shown in Fig. l the circuit is open and in Fig. 2 it is closed. To break the circuit it is merely necessary to open the cover of the box. When the cover is open, the slide and contact I4 may be moved and the cover closed to the 0E position of Fig. l. The entrance Z6 to each contact recess is preferably tapered to facilitate insertion of the movable switch blade. The spring jaws are designed to grip the switch blades so as to provide an effective electrical connection.

When the contacts get overheated there is a tendency to weaken the spring effect and thus decrease the pressure and still further overheat. In fact, the jaws may become so weak and overheated as to destroy the switch.

To avoid this I provide supplemental spring members 3l which are inserted into the recesses l l and l2 alongside of the contact jaws. For convenience these springs 3l mayl have bowed portions 32 which iit in pockets 33 in the jaws. These springs 3i are formed of bimetallic thermostatic material and so constructed that when the contacts heat up the springs expand and increase the pressure against the jaws.

This action enables the ljawsto maintain effective contact pressure on the blades and prevents excessive heating. These auxiliary springs also serve to reenforce the spring jaws.

When the switch is opened and the thermal strips are heated, it might be possible for these bimetallic elements to press the jaws of the contacts together. This is undesirable because the switch blade could be inserted only with great difficulty if the jaws were too close. In order to prevent this, I have provided shoulders 2l in the upper portions of the recesses ll and l2. These shoulders cooperate withextensions 28 on the ends of the contact jaws 9 and l0 to prevent the jaws from being pressed too closely together by the heated bimetallic spring members.

I claim:

l. In a switch, an insulating base having a recess with a tapered entrance, a spring jaw member mounted within said recess, a loosely carried blade mounted to be inserted into said entrance and into said jaw member and bimetallic spring reenforcing means biased between said jaw member and an adjacent wall of said recess.

2. In a switch, an insulating base having a recess with an entrance leading to one end, a spring clip mounted in said recess with outwardly flaring tips near the entrance, said base having shoulders extending between said tips, thermo- 5 static means in the recess for forcing the tips of the clip toward each other when the clip is heated and a switch blade insertable between the tips of the clip through the entrance to said recess.

3. In a switch, a base having a recess open at the back and with an entrance at the front and having shoulders in the recess at opposite sides of the entrance, a U-shaped spring jaw mounted 15 in the recess and having outwardly ilaring tips arranged laterally of said shoulders, thermostatic members on`opposite sides of the jaw in the recess and a switch blade insertable into the entrance and between the tips of the jaw.

4. In a switch, an insulating base having a recess, a spring contact clip mounted within said recess, a switch blade movable into said contact clip and thermostatic springs in said recess on opposite sides ot said contact clip for pressing the contact members against the blade.

5. In a switch, an insulating base having a recess, a spring jaw member mounted within said recess, a blade mounted to be inserted into said jaw member and thermostatic springs loosely mounted in the recess on opposite sides of the jaw member for increasing the pressure of said jaw member against the blade when the jaw member is heated.

RAYMOND N. ROWE. 

